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Wednesday, 11 April 2012

Soldier Insects Secrete Antifungals

Huge ant nest - a large insect community

Many communal insects form large colonies - no doubt benefiting from the advantage this gives them for defence purposes. Anyone who has sat on an ant-hill will attest to the power of the individuals sent out to guard the nest, and there are several other groups of specialised insects within an organised community - otherwise known as 'castes' - each with a particular job to do (Link).
Rather like the principle of mass production 'invented' by Henry Ford 100 years ago, the development of specialised workers is a very efficient strategy to maximising production - in the case of an insect that means more insects!

There is however a drawback to living in a large community. Once an infection enters the community it can rapidly sweep through the nest killing vast numbers - after all, the occupants of an insect nest are closely related and thus have similar ability to fight off infection. Once it has begin it is difficult to stop.

Thrip

A recent paper suggests that insect communities also have an answer to fungal contamination. Thrips are communal insects that have specialised soldiers to guard the colony. It has always been suggested that the large forelimbs of these soldiers offers a physical advantage to them as they fight off invaders, but the authors of this paper suggest that the advantage may not be as big as we thought - when large limbed individuals were matched against smaller limbed thrips they tended to do just as well in a fight!

This begs the question - what are the larger limbs for then? Tests show that the soldier insects can secret antifungal compounds whereas smaller limbed castes cannot. Perhaps then remarkably the main job of a soldier is to fight of fungal invaders rather than larger foe?

This theory is not yet universally accepted but it serves to illustrate the degree of threat fungi exert even on the smallest of creatures, and the extent to which even they have to go to hold fungi at bay.